Functions of gene products from phi X-174 genome have been investigated. 1) The gene A produces two proteins, one enzyme (A) and the other, probably phage structural component (A). A is synthesized from newly synthesized mRNA from the gene A, while A can be synthesized from old mRNA. 2) The gene B product plays a role in the early period of the assembly process. It catalyzes the aggregation of the spike component (G protein) to the capsid protein (F protein). We will continue to work on the identification of functional roles of the gene products of the phi X-174 genome.